Net Ultimate Bearing Capacity For Local Shear Failure Calculator

Formula Used:

\[ q_{nu} = \left(\frac{2}{3} \times C \times N_c\right) + \left(\sigma_s \times (N_q - 1)\right) + \left(0.5 \times B \times \gamma \times N_\gamma\right) \]

Cohesion in Soil (C):

kPa

Bearing Capacity Factor (Nc):

Effective Surcharge (σs):

kPa

Bearing Capacity Factor (Nq):

Width of Footing (B):

Unit Weight of Soil (γ):

N/m³

Bearing Capacity Factor (Nγ):

Net Ultimate Bearing Capacity (qnu):

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1. What is Net Ultimate Bearing Capacity?

Net Ultimate Bearing Capacity is the minimum net pressure intensity that causes shear failure in soil. It represents the maximum pressure that the soil can withstand without failure under local shear conditions.

2. How Does the Calculator Work?

The calculator uses the formula for local shear failure:

\[ q_{nu} = \left(\frac{2}{3} \times C \times N_c\right) + \left(\sigma_s \times (N_q - 1)\right) + \left(0.5 \times B \times \gamma \times N_\gamma\right) \]

Where:

\( C \) — Cohesion in soil (kPa)
\( N_c \) — Bearing capacity factor dependent on cohesion
\( \sigma_s \) — Effective surcharge (kPa)
\( N_q \) — Bearing capacity factor dependent on surcharge
\( B \) — Width of footing (m)
\( \gamma \) — Unit weight of soil (N/m³)
\( N_\gamma \) — Bearing capacity factor dependent on unit weight

Explanation: This formula accounts for the soil's cohesive strength, surcharge load, and the footing's dimensions to determine the maximum load-bearing capacity before shear failure occurs.

3. Importance of Bearing Capacity Calculation

Details: Accurate bearing capacity calculation is crucial for foundation design, ensuring structural stability and preventing settlement or failure of structures built on soil.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. Ensure values are positive and within reasonable ranges for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between local and general shear failure?
A: Local shear failure occurs in soils with some compressibility, showing significant settlement before failure, while general shear failure happens in dense soils with sudden failure.

Q2: How do bearing capacity factors vary?
A: Bearing capacity factors depend on soil properties and are typically determined from established geotechnical tables or formulas based on soil friction angle.

Q3: When is this formula applicable?
A: This formula is specifically designed for local shear failure conditions, typically in soils with moderate compressibility.

Q4: What are typical values for bearing capacity factors?
A: Values vary significantly based on soil type and conditions. Nc typically ranges from 5-40, Nq from 1-40, and Nγ from 0-50.

Q5: How does soil cohesion affect bearing capacity?
A: Higher cohesion values generally increase the bearing capacity, as cohesive soils can withstand greater loads before failure.